Methods and apparatus for biological treatment of aqueous waste

ABSTRACT

A biofilter system of the present invention utilizes an Alternating-Aerobic-Anoxic (AAA) process in a single reactor to provide efficient and cheap removal of carbonaceous materials, nitrogenous materials, and/or mixtures thereof from aqueous waste. The biofilter system of the present invention is particularly suitable for treating aqueous waste from aquaculture, industrial processes and animal husbandry. The biofilter system includes: a main biofilter chamber containing therein aerobic and anaerobic bacteria without physical separation; an inlet port and an outlet port connected to the main biofilter chamber; and a means for oxygenating the aerobic and anaerobic bacteria in the main biofilter chamber, including means for timing the oxygenation of the aerobic and anaerobic bacteria to provide alternating periods of high-oxygen conditions and anoxic conditions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the right of priority under 35 U.S.C. §119 toU.S. Provisional Appl. No. 60/211,302 filed on Jun. 13, 2000, theentirety of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed towards a more efficient and lessexpensive process for biological treatment of aqueous waste and rawanimal waste.

2. Background Art

A balanced nitrogen cycle is important to our environment. However, manyhuman activities have perturbed the nitrogen cycle and causednitrogenous pollution and environmental problems. Fertilizer production,farming of leguminous crops, and fossil fuel combustion contribute to anannual anthropogenic nitrogen fixation of 90, 40 and 20 Tg(N)/yr,respectively. Thus, the overall amount of nitrogen fixation contributedby human activity essentially equals the annual total ofnaturally-occurring nitrogen fixation, i.e., approximately 130 Tg(N)/yr.

Intake of high-nitrate food (e.g., highly fertilized vegetable,livestock fed with high-nitrate forage material or aquaculturalproduction from an aqueous environment of high nitrate concentrations)has been correlated with increased risk to human health. Nitratepoisoning results from the conversion of nitrate to nitrite in the body.Absorption of nitrite into the blood stream produces abnormal hemoglobin(methemoglobin), which is incapable of transporting oxygen. Nitrates inwater or meat are especially hazardous to young infants because theirrelatively high gastric pH facilitates the reduction of nitrate tonitrite by bacteria causing blue baby syndrome. Nitrite can interactwith substrates such as amine and amide to produce N-nitroso compoundsincluding nitrosamines, many of which may cause cancer in many animalspecies.

Ammonia (NH₄ ⁺) is recognized as a toxic compound by the NationalInstitute for Occupational Safety and Health (NIOSH) and theOccupational Safety and Health Administration (OSHA). A number ofammonium compounds, i.e., ammonium acetate, ammonium chloride, ammoniumnitrate, ammonium sulfide, etc., are also toxic to human beings.Ammonium ions in drinking water, where ammonium ions exist inequilibrium with ammonia and hydrogen ions, may not only cause toxicitybut also reduce the disinfecting efficiency of chlorine. Addingadditional chlorine to compensate for the presence of ammonia will alsocause over-disinfection problems such as producing by-products (e.g.trihalomethanes and total organic halogens), tastes and odors,accelerating corrosion, and increasing costs.

The present invention is directed to an efficient and cheap process ofremoving NH₃/NH₄ ⁺, NO₂ ⁻, and NO₃ ⁻ from aqueous waste. The traditionalbiological treatment process uses oxidation methods to remove ammonium.However, oxidation of ammonium does not truly remove it but transformsit into NO₂ ⁻, and NO₃ ⁻, both of which still remain in the system. Abiofilter system of the present invention utilizes anAlternating-Aerobic-Anoxic (AAA) process in a single biologicalfluidized bed reactor to provide efficient and cheap removal ofcarbonacious materials, nitrogenous materials and/or mixtures thereoffrom aqueous waste. This system has great economic advantages over othercurrent nitrogen removal technologies and is believed to be the star oftomorrow. The biofilter system of the present invention is particularlysuitable for treating aqueous waste resulting from aquaculture,industrial processes and animal husbandry.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a biofilter system for removal ofcarbonaceous matter, nitrogenous matter, and/or mixtures thereof, froman aqueous source. The biofilter system includes a main biofilterchamber containing therein aerobic and anaerobic bacteria withoutphysical separation; an inlet port and an outlet port connected to themain biofilter chamber; and a means for oxygenating the aerobic andanaerobic bacteria in the main biofilter chamber, including means fortiming the oxygenation of the aerobic and anaerobic bacteria. The meansfor oxygenating the bacteria may include a pump, an agitator and/or anair diffuser. The biofilter system may further comprise a disinfectionunit, such as, an ozonizer utilizing ultraviolet light. In oneembodiment, the biofilter system may further comprise means formeasuring the level of any one of oxygen, nitrogen, organic carbon,phosphate and pH.

In the biofilter system of the present invention, the bacteria in thebiofilter chamber can be carried by a solid support, such as, forexample, a biotower, a rotating biological contactor, rough stones,slats, plastic media, a reticulated foam particle, a microcarrier and/ormedia particles. In a preferred embodiment, the bacteria are carried byanionic and hydrophilic media particles having a rough surface, such asceramic spheres, with a diameter less than 1 mm, or more preferably,either less than 0.8 mm or less than 0.6 mm. In the alternative, thebacteria can be present in the biofilter in suspension, free of a solidsupport. It is contemplated that the bacteria used in the biofiltersystem of the present invention are capable of growth in aminobenzene,phenol, monoethylamine, diisopropylamine, and/or mixtures thereof.

Another aspect of the invention provides a method for removal ofcarbonaceous matter, nitrogenous matter, and/or a mixture thereof froman aqueous source, wherein the removal is carried out by flowing theaqueous source through a biofilter system of the present invention.Accordingly, the method of the present invention includes the steps of:contacting in a biofilter chamber an aqueous waste with a mixture ofaerobic and anaerobic bacteria; providing high-oxygen conditions;providing anoxic conditions; alternating the step of providinghigh-oxygen conditions and the step of providing anoxic conditions; andmonitoring an outflow from the biofilter chamber for predeterminedlevels of carbonaceous matter, nitrogenous matter or mixtures thereof.

In one embodiment, the outflow is monitored for one or more of nitrogencontent, phosphate content, and organic carbon content. The method ofthe present invention may further comprise the step of recirculating thecontents of the biofilter chamber. In another embodiment, thehigh-oxygen conditions during the high-oxygen periods are uniformthroughout the biofilter chamber. In a further embodiment, thehigh-oxygen conditions are provided with predetermined periodicity. Itis contemplated that high-oxygen and anoxic conditions are provided inalternate periods, wherein, for example, each period lasts between 1 and12 hours. In a preferred embodiment, each of the periods lasts between 2and 9 hours, most preferably with each high-oxygen period lastingbetween 3 and 7 hours, and each anoxic period lasting between 3 and 9hours.

It is preferred that the biofilter system reduce the amount ofcarbonaceous matter, nitrogenous matter, and/or mixtures thereof in theoutflow to no less than approximately 80% of the original amount ofcarbonaceous matter, nitrogenous matter, or mixtures thereof in theaqueous source. It is more preferred for the amount to be reduced by noless than approximately 90%.

According to the method of the present invention, the bacteria utilizedin the biofilter chamber should be capable of growth in aminobenzene,phenol, monoethylamine, diisopropylamine, or mixtures thereof. In oneembodiment, the bacteria may be carried in the biofilter chamber on asolid support, such as, for example, a biotower, a rotating biologicalcontactor, rough stones, slats, plastic media, a microcarrier, and/ormedia particles. In a preferred embodiment, the bacteria are carried byanionic and hydrophilic media particles having a rough surface, such asceramic spheres, with a diameter less than 1 mm, or more preferably witha diameter either less than 0.8 mm or less than 0.6 mm. The bacteria mayalso be present in the biofilter system in suspension, free from a solidsupport.

It is contemplated that the methods of the present invention aresuitable for removal of carbonaceous matter, nitrogenous matter, mattercontaining phosphate, and/or mixtures thereof from aqueous wastegenerated by, for example, aquaculture or industrial processes. Theaquaculture may be carried out in, for example, a tank, a natural pondor lake, a man-made pond or lake, or cages in open waters. Possibleindustrial processes include, for example, effluents from the tanningindustry, the defense industry (e.g. munitions production), the foodindustry, the agriculture industry and the chemical industry (e.g.manufacturing of fertilizers).

An aquaculture system of the present invention includes: an aqueousenvironment; a means for fluidly connecting the aqueous environment witha biofilter system of the present invention; a means for disinfecting anoutflow of the biofilter system; and a means for returning thedisinfected outflow to the aqueous environment. The biofilter system foraquaculture may further include a pump, and/or means for filtering anoutflow from the aqueous environment prior to the outflow entry into thebiofilter system. Accordingly, the aqueous environment may be a tank, aman-made pond or lake, a natural pond or lake, or cages in open waters.The present invention is most particularly directed to a method ofaquaculture wherein fish are grown in the aqueous environment describedherein and the aqueous waste resulting from the aquaculture is treatedby the method for removal of carbonaceous matter, nitrogenous matter,matter containing phosphate, and/or mixtures thereof as described above.

The present invention is further directed towards a biofilter system fortreating animal waste. A biofilter system for treating animal includes:a first vessel having a first inlet port and a first outlet port,wherein the first vessel contains means for degrading waste solidswithin the animal waste and means for separating solid and liquid animalwastes; and a second vessel having a biofilter system of the presentinvention, including a second inlet port fluidly connected to the firstoutlet port of the first vessel. It is contemplated that the effluentfrom the first vessel is aqueous.

The present invention is also directed towards a method of removingcarbonaceous matter, nitrogenous matter, matter containing phosphate,and/or mixtures thereof from animal waste, by passing the waste throughthe biofilter system of the present invention. It is preferred that thebiofilter system reduce the amounts of carbonaceous matter, nitrogenousmatter, matter containing phosphate and/or mixtures thereof in theoutflow by no less than approximately 80% of the original amounts in theuntreated aqueous waste. Most preferably, the amount is reduced by noless than approximately 90%. It is contemplated that the method of thepresent invention is useful for treatment of waste of any animal,preferably a farm animal, such as, for example, a pig, a horse, a goat,a sheep, a cow, a chicken, a turkey, an ostrich, an emu, a llama or analpaca. The biofilter system of the present invention is suitable fortreatment of animal waste comprising no more than approximately 10%solid waste. Preferred, is 5% solid waste, and most preferred is lessthan approximately 1% solid waste.

BRIEF DESCRIPTION OF THE FIGURES

Further features and advantages of the present invention, as well as thestructure and operation of various embodiments of the present invention,are described in detail below with reference to the accompanyingdrawings. The accompanying drawings further serve to explain theprinciples of the invention and to enable a person skilled in thepertinent art to make and use the invention

FIG. 1: Schematic representation of a biofilter system according to thepresent invention.

FIG. 2: Schematic representation of an aquaculture system utilizing thebiofilter system of FIG. 1 according to the present invention.

FIG. 3: Schematic representation of an animal waste treatment systemutilizing the biofilter system of FIG. 1 for treating animal wasteaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention is now described withreference to the figures where like reference numbers indicate identicalor functionally similar elements. Also in the figures, the left mostdigit of each reference number corresponds to the figure in which thereference number is first used. While specific configurations andarrangements are discussed, it should be understood that this is donefor illustrative purposes only. A person skilled in the relevant artwill recognize that other configurations and arrangements can be usedwithout departing from the spirit and scope of the invention.

The following description is modified from Tai, S. K. (1998)“Performance and Kinetics of Alternating, Anoxic/Oxic Fluidized BedReactors,” Ph.D. Dissertation, University of Pennsylvania, Pa.,incorporated herein in its entirety.

As shown in FIG. 1 a biofilter system 100 includes a main biofilterchamber 110 containing therein anaerobic and aerobic bacteria 102without physical separation. An inlet port 104 and an outlet port 106are each connected to main biofilter chamber 110. Means for oxygenatingthe anaerobic and aerobic bacteria 108 includes a means for timingoxygenation, 112. Oxygenating means 108 may be a pump, an agitator,and/or an air diffuser. However, it is contemplated that otheroxygenating means known in the art are suitable for use with thebiofilter system of the present invention.

The biofilter system of the present invention includes an aqueous wasteholding tank 114 for holding liquid waste 116 and/or an effluentcollection tank 118 for collecting treated effluent 119 released frommain biofilter chamber 110. The biofilter system of the presentinvention may further include a first pump P1 for recirculating thecontents of main biofilter chamber 110, and/or a second pump P2 forpumping the liquid waste into the biofilter chamber. The biofiltersystem may also include a means for measuring any one of pH, oxygen,nitrogen, organic carbon and/or phosphate, as represented by referencenumerals 120, 122 and/or 124 in FIG. 1.

It is contemplated that bacteria 102 in biofilter system 100 may becarried by a solid support, such as, for example rough stones, slats,plastic media, microcarriers, media particles, a biotower, or a rotatingbiological contactor. Alternatively, bacteria 102 may grow insuspension, free of solid support.

In general, the biofilter system of the present invention operates asfollows. Liquid waste 116 is pumped by pump P2 from aqueous wasteholding tank 114 into main biofilter chamber 110 via inlet port 104. Abiofilter content 103 of main biofilter chamber 110 is periodicallyoxygenated by means for oxygenation 108. Biofilter content 103 iscirculated through bacteria 102 by recirculation pump P1.

As previously described, bacteria 102 includes aerobic and anaerobicbacteria, which are subjected to alternating high oxygen conditions andanoxic conditions. Depending on the condition and type of bacteria, thebacteria act to “cleanse” the biofilter content 103 of carbonaceusmatter, nitrogenous matter, and/or mixtures thereof. Biofilter content103 may be monitored for desirable levels of oxygen, organic carbon,nitrogen and/or phosphate, as well as pH. Once biofilter content 103 isproperly treated, it is released as effluent 119 through outlet port 106of main biofilter chamber 110 to effluent collection tank 118. Effluent119 may also be monitored for desirable levels of organic carbon,nitrogen and/or phosphate, and may be recirculated into biofilterchamber 110 if the desirable levels are not detected.

As shown in FIG. 2, an aquaculture system 200 of the present inventioncomprises an aqueous environment 202, fluidly connected to a biofiltersystem 100 of the present invention. The outflow of biofilter system 100flows through a means for disinfecting 204 and is thereafter returned toaqueous environment 202. Aquaculture system 200 may further comprise, apump P3 for pumping aqueous waste outflow 201 of aqueous environment 202into biofilter system 100 and/or a pump P4 for pumping disinfectedoutflow 205 back into aqueous environment 202. Aquaculture system 200may further include a means for filtering solid debris 206. The soliddebris filtering means 206 is located between aqueous environment 202and biofilter system 100 to remove debris from the aqueous waste suchthat the aqueous waste is prefiltered prior to entering biofilter system100. Means for filtering solid debris 206 may include, for example, acyclone and/or a microstrainer. Other means for filtering solid debris,well known in the art, are also contemplated for use with theaquaculture system of the present invention.

The aquaculture system may further utilize an oxygenator/carbon dioxidestripper 208, with or without a pump P5, connected to aqueousenvironment 202. In a preferred embodiment, the oxygenator/carbondioxide stripper 208 may also be connected to biofilter system 100providing the means for oxygenating 108 bacteria 102 of biofilter mainchamber 110, as shown in FIG. 1.

Another embodiment of the present invention is an animal waste treatmentsystem 300 that utilizes a biofilter system 100 for treating animalwaste 300, as shown in FIG. 3. In this embodiment, a solid and liquidanimal waste slurry 301 is introduced into a first vessel 302 where thesolids are further degraded, producing a biogas, such as methane. Meansfor degrading solids in the animal waste slurry may include enzymaticdigestion, mechanical shearing, and any other method known in the artfor degrading solid waste. First vessel 302 preferably contains a meansto separate solid and liquid waste (not shown). Means for separatingsolid and liquid wastes includes filtering, centrifuging, and any othermethod known in the art for separating solids and liquids. A liquidanimal waste 303 is passed into a second vessel 304 which includes abiofilter system 100 of the present invention.

In one embodiment, an animal waste treatment system 300 of the presentinvention can further comprise means for capturing the biogas 306 (notshown). Such biogas capturing means are well known to those of ordinaryskill in the art. In another embodiment, first vessel 302 also utilizesa means for discarding waste solids 308 (not shown) to degrade wastesolids which remain after the degradation process.

Treatment technologies of nitrogen removal vary with differentnitrogenous compounds. A list of these technologies are shown in Table 1below. Among them, biological treatment is considered the mostadvantageous method due to its efficiency, simplicity and low cost. Forthe biological treatment, two major biological mechanisms, nitrificationand denitrification, are responsible for the transformation of NH₃/NH₄⁺, and NO₃ ⁻ in the presence of appropriate bacteria. Based oncharacteristics of the bioreactor, the biological methods can becategorized into three major forms: suspended-growth reactor,attached-growth reactor, and fluidized-bed reactor.

TABLE 1 Treatment technologies for nitrogen removal Nitrogenous compoundRemoval Method Reference NH₃ Air Stripping Diamadopoulos, 1994 NH₃Dielectric barrier discharges (DBDs) Chang and Tseng, 1996 NH₃/NH₄ ⁺Artificial wetland Sumrall et al., 1994; Farahbakhshazad and Morrison,1997 NH₃/NH₄ ⁺ Biological treatment (nitrification) Hem, et al., 1994;Cecen and Orak, 1996 NH₃/NH₄ ⁺ Ion exchange process Lin and Wu, 1996(a)NH₃/NH₄ ⁺ Electrochemical oxidation method Lin and Wu, 1996(b) NO₂ ⁻Electrochemical oxidation method Lin and Wu, 1996(c) NO₂ ⁻Electrochemical reduction method Genders et al., 1996 NO₂ ⁻ Biologicaltreatment (nitrification) Gee et al., 1990 NO₂ ⁻ Biological treatment(denitrification by a Rahmani, et al., 1995 submerged granularbiofliter) NO₃ ⁻ Biological treatment (denitrification by a McCleaf andSchroeder, 1995; membrane-fixed biofilm reactor) Reising and Schroeder,1996; Fuchs, et al., 1997 NO₃ ⁻ Biological treatment (denitrification bya Liessens, et al., 1993; fluidized-bed reactor) Lazarova, et al., 1994NO₃ ⁻ Electrochemical reduction method Genders et al., 1996 NO₃ ⁻ Ionexchange Van der Hoek and Klapwijk, 1989; Clifford and Liu, 1993; Brown,1995 NO_(x) Ammonia radical (plasma) injection Chess, et al., 1995 (NOand process NO₂)

In a suspended-growth reactor, the biological sludge (microorganisms)and wastewater (containing organic and mineral compounds as food formicroorganisms) are mixed. The mixture is usually agitated and aerated,and, under such conditions, growth of microorganisms is stimulated. Theindividual organisms gradually clump together (flocculate) and form anactive mass of microbes (activated sludge).

In an attached-growth reactor, there are essentially three types ofattached-growth processes which utilize solid supports, i.e., tricklingfilter, biotower and rotating biological contactor (RBC). In suchsettings, microorganisms attach and live on the medium and extract thenutrient from the wastewater flow (a process of removing chemicalcompounds from the wastewater) passing by them. A trickling filter isabed of course material (e.g., stones, slats and plastic media) andwastewater is passed through it. Biotowers are also trickling filters,but in the shapes of high towers. A RBC uses flat disks that range indiameter from 2 to 4 m and up to 1 cm in thickness as the solid supportfor microorganisms to attach. The disks are mounted on a common shaftthat rotates at approximately 1 to 2 rpm. Trickling filters andbiotowers are typical fixed-biofilm reactors, while a RBC is treated asa special adaptation of the attached-growth process.

A fluidized-bed reactor is similar to the attached-growth reactor inalso being a biofilm reactor. However, the difference between theattached-growth reactor and the fluidized-bed reactor is that thebiofilm media of the latter are not fixed but fluidized. The advantagesof a fluidized-bed reactor over suspended-growth and attached-growthreactors include: high biomass concentrations and surface areas, lesssusceptibility to sudden changes in load or temperature, successfulcarbon and nitrogen removal from municipal wastewater, the eliminationof any problems and costs caused by sludge, and less expense based onsavings in reactor space and rapid treatment time. The fluidized-bedreactor is 18 times more efficient than the packed-column(attached-growth) reactor in terms of nitrate removal of per unitreactor volume. A comparison between suspended-growth and fluidized-bedreactors showed the fluidized-bed process can obtain the same level oftreatment in less than 5 percent of the space and 5 percent of the timerequired for a three-sludge system.

The biological fluidized-bed (BFB) reactor was first developed fordenitrification of nitrified sewage effluents. Later on, they wereapplied to carbonaceous oxidation and nitrification of settled sewage.The BFB reactor was used in an number of studies on nitrification.

The media of a BFB reactor usually have a light weight and a size in therange of 0.2 to 1.0 mm. At the beginning of operating a BFB reactor, theparticles are expanded in a column by an upward flow of recirculation tothe point at which the upward force is equal to the downward gravity.However, as the bacteria grow as a biofilm around the particle,increasing biofilm volume will continue to expand the bed. Therefore, atthe steady state, where cell growth equals the rate the cells are washedoff by the surface sheer, the bed may be at an undesirable height. As aresult, to remove the excess biomass, particles should be taken out ofthe reactor and washed when needed.

The alternating-aerobic-anoxic (AAA) process has two process reactions,i.e., an aerobic process and an anoxic process. Under the aerobicconditions, NH₄ ⁺ (or also NO₂—N) is first biologically oxidized to NO₃⁻—N via nitrification. In the next anoxic stage, NO₃ ⁻—N is denitrifiedand the end product is nitrogen gas. Because these two reactions haveopposite demand for oxygen, each reaction cannot occur simultaneously inthe same reactor. Therefore, each reaction must occur in either analternate space or time.

Initially, the AAA process was developed in a configuration of spatialalternation. In such a process, nitrification and denitrification occursindividually in physically separate zones of the tank or separate tanksof the system. This idea mainly originated from the success of efficientnitrogen removal by building aerobic and anaerobic zones in sequence inthe treatment system. Designs combining nitrification anddenitrification stages in various spatial configurations have beenstudied and applied in many treatment systems. Two different three-stagesystems featured continuous stages of carbonaceous removal,nitrification, and denitrification in space. One approach known in theart utilized a supplemental organic carbon source, but another approacheliminated this need by introducing the influent organic matter into thedenitrification basin. The latter approach utilized a singlereactor-clarifier system with sequential basins in the order ofanaerobic, aerobic, anaerobic, and aerobic. This process, known asBardenpho, can remove 90 to 95% of nitrogen and precipitate up to 97% ofphosphorus without external supply of organic carbon. The combined N/D(Nitrification/Denitrification) system uses the first two stages of theBardenpho process and its removal efficiency was evaluated at 97% of theinfluent total kjedhal nitrogen (TKN) and 93% of the influent chemicaloxygen demand (COD).

A more recent AAA process includes periodic aeration in the system. In1975, a two-basin, single-sludge system was proposed. This systemcreates an alternating aerobic-anoxic environment in each basin forefficient nitrogen removal and shares much similarity with the latersuccessful model of BIODENIPHO 9. BIODENIPHO is the trademark for thepatented process developed by I. Kruger Systems and the Department ofEnvironmental Engineering at the Technical University of Denmark. TheBIODENIPHO process contains two aerobic/anoxic tanks and performsnitrification and denitrification in a semi-batch manner by periodicallyaerating the tanks and changing the path of flow.

Although the treatment target of a AAA process is NH₂ ⁺, it is also truethat phosphorus removal can be accomplished in the AAA process. Thephosphorus removal process usually contains an anaerobic stage, where nonitrate and dissolved oxygen should exist, followed by an aerobic stage,where PHB (poly-β-hydroxybutyrate) is oxidized and excess phosphate ismoved by the bio-P (biological phosphorus removal) bacteria. Based onthe above conclusion, a typical spatial alteration process for removingboth phosphorus and nitrogen is usually composed of an anaerobic tank,an anoxic tank and finally an aerobic tank.

The kinetic model for the complete mixed AAA process is based on thestructured biomass model and assumes that the heterotrophic biomasswithin this system is divided into three components—stored mass, activemass, and inert mass. Their production rates are described by the Monodfunction. Two important process variables are emphasized in this model.One is the aeration fraction (AF), which determines the ammonia andnitrate level. The other one is the cycle time ratio (CTR, or the ratioof cycle time to HRT). For example, one AAA system has a 2-hour-on and2-hour-off cycle and an HRT of 16 hours, so the CTR is (2+2)/16 or 0.25.CTR represents the degree of non-steady-state conditions by intermittantaeration. A simplified form of this earlier model assumes first-orderrate equations for carbon oxidation (aerobic and anaerobic) andnitrification.

A simplified ASM1 (Activated Sludge Model No. 1) was used to describethe nitrogen dynamic in the BIODENIPHO system. ASM1 was developed by theInternational Association on Water Pollution Research and Control(IAWPRC) task group and became the standard model of the single-sludgesystem for carbonaceous removal, nitrification and denitrification. Itconsists of seven basic processes: aerobic growth of autotrophicbiomass, aerobic growth of heterotrophic biomass, anoxic growth ofheterotrophic biomass, decay of autotrophic biomass, decay ofheterotrophic biomass, hydrolysis of entrapped particulate organicmatter, and hydrolysis of entrapped organic nitrogen. By using thismodel, a novel control strategy for improved nitrogen removal in analternating activated sludge process was possible.

Mathematical modeling and computer simulations were used to modify ASM1for a bench-scale activated sludge reaction system. The majordifferences between ASM1 and this modified model are the state variablesof dissolved oxygen (DO) and nitrite, the distinction between aerobicheterotrophic yield and anoxic heterotrophic yield, and the correlationbetween temperature, pH (and alkalinity), and the process kinetics. Itwas proved that prediction by this revised model agrees well with theexperimental data.

According to the present invention, the AAA process is combined with asingle-reactor biological fluidized bed system. The biological fluidizedbed system, with great advantages of less space and no sludge, isbecoming very important to the future practice of the AAA process.

The major feature of the AAA process is alternating aeration. A propercombination of aeration and non-aeration time is crucial to an optimalperformance of the AAA process. For an easily biodegradable organiccarbon source (e.g., glucose), free ammonium can be removed efficientlyat aeration/non-aeration ratios, different aeration or non-aeration timemay cause the AAA process to perform differently, depending on how theaeration or non-aeration time affects it. For example, 4-hr on/2-hr off,with the ratio of 2, has insufficient non-aeration time (2 hours) forcomplete denitrification. Although 9-hr on/4-hr off has a ratio of 2.25,its non-aeration period (4 hours) is increased and greatly improvestotal nitrogen removal of the AAA process.

As for a slowly biodegradable (under anoxic conditions) organic carbonsource (e.g., aniline), which has a low denitrification rate, thenon-aeration time should be accordingly increased. Consequently, anaeration/non-aeration ratio less than 1 is a common design parameter forthe AAA process. The disadvantage of a long aeration duration, causingreduction of aeration/non-aeration ratio, is to produce more NO₃ ⁻—Nthan the denitrification process can reduce.

This invention provides processes incorporating the AAA process inremoving complex organic compounds, such as, for example aniline oraminobenzene. Aniline is a complex toxic compound which is used in anumber of industrial manufacturing processes. As the regulation ofeffluent toxicity is getting much stricter, the current invention, whichprovides economic and efficient ways to detoxify a broader range oftoxic and hazardous compounds, can be of great commercial benefit inindustry.

Aquaculture has been growing fast in recent years for two reasons:shortage of naturally-occuring seafood stocks caused by humanactivities, e.g., ocean pollution, over-fishing, etc., and increaseddemand for fish. Aquaculture requires purity of water, and generatesnitrogenous and organic aqueous waste. It is known that ammonia andnitrous acid (HNO₂) are toxic to fish and a high nitrate concentrationmay cause fish to develop Pseudomonas skin infections. The presentinvention solves the problem of nitrogenous (NH₄ ⁺, NO₂ ⁻—N and NO₃ ⁻—N)pollution caused by a high density of fish, such as, for example bass ortilapia. An aquaculture system according to the present inventionremoves excess organic and nitrogenous waste, and recycles the water inthe aquaculture environment, creating a more efficient and economicaquaculture system.

In a further embodiment of the present invention, biofiltration is usedto purify raw animal waste. Accordingly, the solids in the raw waste mayfirst be degraded, and the resulting liquid (aqueous) waste is thenpurified by the methods of the present invention. The degradation of thesolids in the raw waste can be accomplished by a variety of techniques,such as, for example, shredding, enzymatic degradation, homogenizing,and other techniques well known to those of ordinary skill in the art.Particulate matter may also be removed from liquid waste.

In a preferred embodiment, the animal waste treatment system of thepresent invention is physically enclosed. The advantages of such systemsinclude reduced odor, reduced possibility of contaminated surroundingsand reduced possibility of overflow due to, for example, rain.

It will be readily apparent to one of ordinary skill in the relevant artthat other suitable modifications and adaptations to the methods andapplications described herein may be made without departing from thescope of the invention or any embodiment thereof. Having now describedthe present invention in detail, the same will be more clearlyunderstood by reference to the following examples, which are includedherewith for purposes of illustration only and are not intended to belimiting of the invention.

EXAMPLES Example 1 Experimental Material and Analytical Equipment

Experimental materials and analytical equipment were used to create anexample of a biofilter system according to the present invention.

Air Diffuser: Made of wood and purchased from a regular aquarium store.

Air Pump: The model of Silenger by Penn-Plax (Garden City, N.Y.).

ChronTrol XT: The ChronTrol XT (ChronTrol Corporation, San Diego,Calif.) is a programmable, microprocessor-based timing device. It caneasily be programmed to switch circuits on and off at specific times anddates, for durations, on a cycle, or from external devices attached toits optional input connector. In this example, the ChronTrol XT is usedto adjust the aeration modes and feeding rates.

Constant Temperature Cabinet (Stabil-Therm) and Muffle Furnace(M15a-2A): Both models are made by Blue M (Blue Island, Ill.).Measurement of mix liquid volatile suspended solids (MLVSS) and attachedvolatile suspended solids (AVSS) will follow the standard method 2540 E(17th edition, 1989).

DC-80 Total Organic Carbon Analyzer: A modular TOC analysis system madeby Rosemount Analytical, Inc. (Santa Clara, Calif.). It is equippedalong with Balston 78-30 TOC Gas Generator (Balston Inc., Havenhill,Mass.). Before injection, filtered sample is acidified with phosphoricacid and sparged for a few minutes to remove inorganic carbon. Injectionvolume is 200 μl for the detection range of 10-800 mg/l TOC. Oxidationreagent is made of 20 grams of Potassium Persulfate (K₂S₂O₈) dissolvedin 1 liter of reagent water and then added 1 ml of concentratedphosphoric acid. TOC is oxidized by ultraviolet promoted persulfateoxidation and measured by infrared detection.

DR/4000 Spectrophotometer: Manufactured by HACH (Loveland, Co.) and isused for measuring NH₃—N, NO₂ ⁻ and NO₃ ⁻; Salicylate Method is used formeasuring NH₃—N at the concentration level of both 0 to 2.5 mg/l NH₃—Nand 0 to 50.0 mg/l NH₃—N. Diazotization Method is USEPA approved andwastewater analysis for low range nitrite (0 to 0.3000 mg/l NO₂ ⁻—N),while Ferrous Sulfate Method is for high range nitrite (0 to 250 mg/lNO₂ ⁻—N). Chromotropic Acid Method is to measure nitrate in the range of0 to 250 mg/l NO₃ ⁻—N).

Feeding Apparatus: MasterFlex pump controller by the Cole-ParmerInstrument Company and clear flexible plastic laboratory tubing (TYGON®)(inside diameter of 4.8 mm and outside diameter of 7.9 mm) by the NortonCompany (Wayne, N.J.).

Gel-Filled Combination pH Electrode: The ORION Gel-Filled CombinationElectrode is designed for routine pH measurements under ruggedconditions. The sealed reference section, permanently filled with a Kclgel, never needs refilling. A portable pH/ISE model by ORION (Model290A) is chosen as the meter.

Microcarrier: 70 Mesh ceramic spheres (MACROLITE®) by Kinetico Inc.(Newbury, Ohio).

Mineral Solution: It is diluted from the concentrate with distilledwater before use. The concentrate contains the mineral mixture at aconcentration for metabolizing 5000 ppm C by microorganisms. It is madein advance and kept in the refrigerator. The dilution ratio depends onhow much carbon will be metabolized.

Recirculating Apparatus: MasterFlex pump controller and flexible tubing(NORPRENE®) (inside diameter of 7.9 mm and outside diameter of 11.3 mm),both by the Cole-Parmer Instrument Company (Vernon Hills, Ill.).

Synthetic Feeds: It is diluted from the concentrate with distilled waterbefore use. The concentrate contains the mix of 5000 ppm of C₆H₁₂O₆—Cand 1250 ppm of (HN₄)₂HPO₄—N.

Wheaton 60 Second BOD System with LED: This system (Wheaton Instruments,Millville, N.J.) is used to read the dissolved oxygen (DO)concentrations. The BOD probe has a basic construction consisting ofthree electrodes and a thermistor for temperature compression.

Example 2 Method of Comparing the Purification of Aqueous Waste UnderConstant High-Oxygen Conditions and Under Alternating High-Oxygen andAnoxic Conditions

Two biofilter systems similar to those shown in FIG. 1 and utilizing theexperimental materials and analytical equipment of Example 1 were setup. One was tested under continuous aeration, and the other underalternating aeration. Feed solution consisting of approximately 50 mg/lC₆H₁₂O₆—C, 15 mg/l (HN₄)₂HPO₄—N and mineral nutrients was placed in arefrigerator. The feed solution was pumped into the reactor at a rate ofapproximately 4 ml/min for a length of 5 seconds at intervals of 25seconds. The recirculation rate was about 280 ml/min, which expanded thebed height to a ratio of approximately 35 cm to 24 cm, or 1.46.

Inoculum was obtained from the activated sludge cultivated on glucose.During the period of the experiment, microorganisms may appear on theinner wall of the feeding tubing which portion is exposed in the air.Therefore, frequent cleaning of that portion of the tubing is needed.Also due to this fact, the influent concentrations should be measured atthe inlet of the reactor, not from the reservoir in the refrigerator,for more realistic measurements.

Effluent was collected for 24 hours daily as a composite effluent. Toreduce the influence from exposure to the open air, such acts as addinga cover or keeping at a lower temperature are helpful for stability ofthe composite effluent. Composite concentrations of TOC, ammoniumnitrite, and nitrate in the effluent were measured. The steady state wasindicated by relatively stable outcomes of the composite concentrations.The steady state of these two reactors was achieved before any analysisstarted.

Different aeration/non-aeration modes were applied to the AAA process: 2hrs/2 hrs, 3 hrs//3 hrs, 4 hrs/4 hrs, 5 hrs/5 hrs, 6 hrs/6 hrs. A shiftbetween each two aeration/non-aeration modes required an acclimationperiod for the microorganisms to adjust to a new environment. Comparingperformances between the continuous aeration process and the AAA processwas based on their nitrogen removal efficiency, which data were derivedfrom the composite concentrations of NH₄ ⁺, NO₂ ⁻, and NO₃ ⁻ in theeffluent. For the AAA process, the kinetic study was conducted for eachaeration/non-aeration cycle, in which samples were withdrawn at hourlybases from the upper liquid in the reactor for measurement of TOC,ammonium, nitrite, and nitrate concentrations. In this way, mechanismsof the nitrification and denitrification processes were investigated.

Example 3 The Results of Purifying Aqueous Waste Under ConstantHigh-Oxygen Conditions and Under Alternating High-Oxygen and AnoxicConditions

Based on the low effluent NH₄ ⁺—N concentration, both the continuousaeration and AAA processes performed quite well. However, if theeffluent total nitrogen concentrations were examined, all the AAAprocesses, 2-hr on/2-hr off, 3-hr on/3-hr off, 4-hr on/4-hr off, 5-hron/5-hr off, and 6-hr on/6-hr off (on: aeration on; off: aeration off ornon-aeration), had lower effluent total integer concentration than thatof the continuous aeration process. The effluent total nitrogenconcentration obtains the most contribution from NO₃ ⁻—N. Since both thecontinuous aeration and AAA processes had low effluent NH₄ ⁺—N and NO₂—Nremoval concentrations, it implied that in the AAA process, NO₃—N hadbeen denitrified at the non-aeration stage and removed from the system.The combination of nitrification and denitrification in the AAA processthus proved to have the added advantage of removing ammonium as well astotal nitrogen (NH₄ ⁺—N, NO₂ ⁻—N and NO₃ ⁻—N) over conventionalnitrification methods. As well, the data supported the BFD reactor as afeasible and contributive to the performance of the AAA system.

Quantitative analysis of denitrification can be done by using a nitrogenbalance which is established by the following equation.

(feed NH₄ ⁺—N)*(feed rate)=(effluent NH₄ ⁺—N+NO₂ ⁻—N+NO₃ ⁻—N)* (effluentrate)+(effluent VSS)*(14/113)*(effluent rate)

Since feed rate equals effluent rate, the above formula can besimplified as

influent NH₄ ⁺—N=[(effluent NO₂ ⁻—N+NO₂ ⁻—N+NH₄ ⁺—N) or (effluentn=total nitrogen)]+(effluent VSS)*14/113

The continuous aeration process gave a good balance of the nitrogenconcentrations: influent NH₄ ⁺—N, approximately 15 mg/l, effluent totalnitrogen, in the range of 12 to 13 mg/l, MLVSS, at the average of 8mg/l. Any deviation from the balanced nitrogen equation in the AAAprocess indicates the production of nitrogen gas from denitrification.

Organic carbon, C₆H₁₂O₆—C in this experiment, had two outcomes in theAAA process. First, it was biologically oxidized at the aeration stagein the presence of oxygen and microorganisms. Secondly, organic carbonwas one of the substrates for heterotrophic denitrifying bacterial.Based on the following denitrification reaction:

NO₂ ⁻—N+2C₆H₁₂O₆—C+H⁺→0.5N₂+1.25H₂CO₃+0.5H₂O,

1 mg NO₃ ⁻—N will react with 1.07 mg C₆H₁₂O₆—C. If 1 mg NO₃ ⁻—N iscompletely converted from the same amount of NH₄ ⁺—N, it indicates thatfor treating 1 mg NH₄ ⁺—N by the AAA process, at least 1.07 mg C₆H₁₂O₆—Cis required in the system. Because of these two outcomes for organiccarbon in the AAA process, the AAA process achieved TOC removalefficiencies comparable to those of the continuous aeration process.

A series of kinetic studies were done on the aeration modes of 3-hron/3-hr off, 4-hr on/4-hr off, 5-hr on/5-hr off, and 6-hr on/6-hr off,to determine optimal on/off timing. A common characteristic of thekinetics of the AAA process was found among those different aerationmodes. At the beginning of each cycle (aeration on), nitrate (comingfrom oxidation of NH₄ ⁺—N or nitrification) began to accumulate in thesystem and its concentration in the effluent was increased. During thesame period, nitrite low concentration was low, indicating itstransience in the nitrification process. The concentrations of NH₄ ⁺—Nstayed low (around 2 mg/l) because of nitrification.

As the non-aeration period started, theoretically, nitrate concentrationwas expected to drop due to denitrification, and ammonium was expectedto accumulate because no nitrification takes place. However, thesephenomena were not immediately observed as the air pump was shut off,since previous aeration caused the system to be saturated with dissolvedoxygen and thus allowed nitrification to go on after aeration wasterminated. It took about 1 to 2 hours for the dissolved oxygen in thereactor to be depleted, and for the denitrification process to takeover. From this point on, the nitrate concentration started to decreaseand the ammonium concentration increase. Meanwhile, the nitriteconcentration exhibited a bi-phasic response, rising first buteventually dropping, indicating that nitrite was only a transientproduct of the denitrification process. It was found that a 2-hournon-aeration period might not be long enough for the denitrificationprocess to start or fully function. With an influent containing 50 mg/lTOC and 15 mg/l NH₄ ⁺—N, there was little difference among the carbonand nitrogen removal efficiencies by the aeration modes of 3-hr on/3-hroff, 4-hr on/4-hr off, 5-hr on/5-hr off, and 6-hr on/6-hr off. Since allthese processes had an aeration/non-aeration ratio of 1, further studieswere undertaken to investigate the effect of ratios other than 1.

Other parameters were investigated, including anoxic TOC removal. Theformulae derived from an analogous procedure to the technique ofestimating the dead volume in a CFSTR (continuous-flow, stirred-tankreactor) system were applied. Equations are as follows.

Anoxic TOC removal rate in the AAA Process: The CFSTR dilution curve wasused to predict the effluent TOC concentration at time t_(i),C_(p)(t_(i)), with the assumption that the organic carbon does notundergo any reaction:${{C_{p}( t_{i} )} = {C_{l} - {( {C_{l} - C_{g}} ){\exp ( \frac{t_{i}}{\theta} )}}}},{i = 0},1,2,{{\ldots \quad n} - 1}$

where θ is the reactor empty bead hydraulic reunion time, hour, andt₀=0. The difference between C_(p)(t_(i)) and C₀(t_(i)), the effluentTOC concentration observed at time t₀, is taken as the TOC removed attime t_(n).

C_(p)(t _(i))=C_(p)(t _(i))−C₀(t _(i))

The anoxic TOC removal rate over a time interval (t_(i), t_(i−1)),U_(anoxic)(t_(i−1)), is calculated as:

${U_{anoxic}( t_{i} )} = \frac{\lbrack {{C_{R}( t_{i + 1} )} - {C_{R}( t_{i} )}} \rbrack}{\lbrack {{AVSS} \times ( {t_{i + 1} - ( t_{i} )} \rbrack} }$

where AVSS is the attached volatile suspended solids, mg/l. The moreanoxic TOC removal rate, U_(anoxic) is calculated as:$U_{anoxic} = \frac{\sum{U_{anoxic}( t_{i - 1} )}}{n}$

Nitrification Rate in the AAA Process: The formula predicting thedisappearance of NO₃ ⁻—N from the system, where nitrification is assumednot to take place, is used to predict the effluent NO₃ ⁻—N from thesystem, where nitrification is assumed to take place, is used to predictthe effluent NO₃ ⁻—N concentration at time t₀, n−1, N_(p)(Ti):${{N_{p}( t_{i} )} = {N_{0}{\exp ( {- \frac{t_{i}}{\theta}} )}}},{i = 0},1,2,{{\ldots \quad n} - 1}$

where N₀ is the effluent NO₃ ⁻—N concentration at time t_(p), N_(p)(i₁)is:

N_(p)(t _(i))=N₀(t _(i))−N_(p)(t _(i))

where N₀(t_(i)) is the effluent NO₃ ⁻—N concentration observed at timet_(i), mg/l. The nitrification rate over a time interval (t_(i),t_(i−1)), U_(N)(t_(i−1)), is calculated as:${U_{N}( t_{i - 1} )} = \frac{\lbrack {{N_{g}( t_{i + 1} )} - {N_{R}( t_{i} )}} \rbrack}{\lbrack {{AVSS} \times ( {t_{i + 1} - ( t_{i} )} \rbrack} }$

The mean nitrification rate, U_(N), is calculated as$U_{N} = \frac{\sum{U_{N}( t_{i - 1} )}}{n}$

Denitrification Rate in the AAA Process: The formula predicting thedisappearance of NO₃—N from the system, where denitrification is assumednot to take place, is used to predict the effluent NO₃ ⁻—N concentrationat time t₀, N_(p)(t₀):${{N_{p}( t_{i} )} = {N_{0}{\exp ( {- \frac{t_{i}}{\theta}} )}}},{i = 0},1,2,{{\ldots \quad n} - 1}$

The NO₃ ⁻—N concentration consumed by denitrification at time t₀,N_(p)(t₀) is:

N_(R)(t _(i))=N_(P)(t _(i))−N₀(t _(i))

The denitrification rate over a time interval (t_(i), t_(i−1)),U_(DN)(t_(i−1)), is calculated as:${U_{DN}( t_{i - 1} )} = \frac{\lbrack {{N_{g}( t_{i + 1} )} - {N_{R}( t_{i} )}} \rbrack}{\lbrack {{AVSS} \times ( {t_{i + 1} - ( t_{i} )} \rbrack} }$

The mean denitrification rate, U_(DN), is calculated as:$U_{DN} = \frac{\sum{U_{N}( t_{i + 1} )}}{n}$

Note that the nitrification rate and the denitrification rates discussedherein are the nitrate production rate and the nitrate reduction rate,respectively. These rates may appear in some other cases with differentunits or definitions. Reaction rates also vary depending upon reactionconditions.

Example 4 Removal of a Nitrogen-Containing Organic Chemical from AqueousWaste Under Alternating High-Oxygen and Anoxic Conditions

The feasibility of using the AAA process to remove more complicatedtoxic compounds containing both nitrogen and organic carbon was tested.As shown above by both the theory and experimental data, the AAA processcan not only deal with nitrogenous compounds (especially NH₄ ⁺, NO₂ ⁻and NO₃ ⁻) but at the same time remove the organic carbon. Both effectslead to the potential broad application of the AAA process. Secondly, aninternal carbon source means no need for external carbon usage and thusreduces the operating cost. When a compound consisting of both nitrogenand organic carbon undergoes a denitrification reaction, thebiodegradability of the organic carbon becomes critical to thedenitrification rate.

Compared with glucose, the aromatic structure of aniline makes itselfsomehow difficult to decompose. Therefore, a lower denitrification rateis expected in the AAA process. Reduced denitrification efficiencyresults in a need for a longer non-aeration duration for sufficientdenitrification, thus requiring a lower aeration/non-aeration ratio.Different aeration/non-aeration ratios, including 1, >1, and <1, weretested for the optimal performance of the AAA process. The performancesof two AAA processes on different influent contents (one is glucose plusNH₄ ⁺ and the other is aniline) was also compared.

Experimental material and analytical equipment: In addition to thematerials and methods listed in previous Examples, some changed or addeditems are described below.

Ammonia Ion Selective Electrode: The ammonia probe provides analternative to DR/4000 Spectrophotometer for a quicker analysis ofammonium concentration. This gas-sensing probe by Accumet utilizes apre-bonded semi-permeable membrane cap which separates the electrodes'internal fill solution from the sample solution. The outer body isconstructed of durable, break-resistant polypropylene. As EA 920Expandable Ion Analyzer by ORION is chosen as the measuring meter.

Rapid Distillation Apparatus: The Labconco (Kansas City, Mich.) RapidDistillation Apparatus is designed expressly for rapid, semi-automaticsteam distillation from sulfuric acid digest prepared fromnitrogen-bearing materials such as feeds, grains, soils, water effluent,organic waste, etc. It can be used for micro or macro levels of nitrogendetermination.

The experimental procedures were as described above. The mainconstituent of the influent was C₆H₅NH₂, which has the carbon/nitrogenratio of 74/14. No external organic carbon source was added. TotalKjedahl nitrogen (TKN), a measure of the total organic and ammonianitrogen, was measured to determine the influent organic carbon and itsfate in the AAA process. Two influent aniline concentrations wereapplied to the AAA process. For each concentration, differentaeration/non-aeration ratios were tested. As before, the compositeeffluent concentrations of TOC, NH₄ ⁺—N, NO₂ ⁻—N and NO₃ ⁻—N weremeasured daily and the kinetic study was conducted for detailed data ofnitrification and denitrification mechanisms. Batch experiments of toxicTOC removal and anoxic denitrification were used to examine anyinhibition effects by aniline.

Although the influent contained mainly aniline and mineral nutrients,there was still trace amount of free NH₄ ⁺ detected in the influent.These low concentrations were deducted from both sides of the nitrogenbalance to exclude their effects. Influent TOC and organic nitrogen wasdetected at a stable ratio (theoretically, C/N: 72/14) as the chemicalstructure of aniline indicates. In the case of continuous aeration withan influent concentration of approximately 18 mg/l org N and 1 mg/l NH₄⁺—N, a balanced nitrogen conversion was established by effluent 17 mg/ltotal nitrogen, 0.4 org. N and 20-30 mg/l MLVSS. For the results of theAAA process, the deficit in the nitrogen balance equation indicated thatpart of the influent aniline was successfully removed as nitrogen gas.As the aeration/non-aeration ratio dropped from 6-hr on/6-hr off, 4-hron/6-hr off, 4-hr on/8-hr off to 4-hr on/10-hr off, the effluent totalnitrogen was correspondingly decreased, or the total nitrogen removalefficiency was improved. The kinetic study of 6-hr on/6-hr off showedthat denitrification of nitrate and nitrite was interrupted bytermination of non-aeration period and only 40% of total nitrogen wasremoved. Therefore, an aeration/non-aeration ratio less than 1 willallow longer non-aeration period to denitrify accumulated NO₃—N from theaeration stage and improve the total nitrogen removal efficiency.However, the compensation for extended non-aeration period wasaccumulation of effluent aniline.

The aeration/non-aeration regimen of 4-hr on/4-hr off, with the ratio of1, had very different kinetic results from the other AAA processestested. NO₂ ⁻—N was the main effluent constituent through the whole AAAprocess, while NH₄ ⁺ and NO₃ ⁻—N were at low concentrations. Oneproposed mechanism for this phenomenon was that both aeration andnon-aeration periods were insufficient for complete nitrification anddenitrification processes, thus leading to a bypass from NH₄ ⁺—N to NO₂⁻—N and finally nitrogen gas.

Higher aniline concentrations were also tested, with twoaeration/non-aeration ratios. Both 6-hr on/6-hr off and 9-hr on/9-hr offhad TOC removal efficiencies of over 90%. The total nitrogen removalefficiency of 9-hr on/6-hr off was lower than that of 6-hr on/6-hr off.Compared with lower concentrations, the AAA process still has excellentcarbon and nitrogen removal performance of higher influent anilineconcentrations.

Studies show that biological transformation of aniline involves, at theearly stage, carbonaceous removal by heterotrophic bacterial (undertoxic conditions) and at the same time releasing NH₄ ⁺—N. NH₄ ⁺ is thenremoved by nitrification and denitrification as usually seen in the AAAprocess. It has also been demonstrated that a high initial anilineconcentration does not affect the heterotrophic activity (toxic anilinedegradation to release NH₄ ⁺). A kinetic study of batch nitrificationunder toxic conditions, discussed in the thesis on which the presentinvention is based (see supra), shows that aniline is degraded at a highconcentration such as 25 mg/l TOC. However, aniline is too toxic tonitrify microorganisms and their activities are reduced by increasedaniline concentrations. The effect of high initial concentrations of 250and 425 mg/l aniline in an activated sludge system has been described:although the aniline concentration falls very rapidly, effectivenitrification does not take place at 26 hours. As a result, upper limitsshould be put on the influent aniline concentrations for an efficientAAA process. An anoxic batch experiment of aniline showed extremely slowdenitrification process (reduction of NH₄ ⁺—N and NO₃ ⁻—N) on variousinitial aniline concentrations from a low of under 20 mg/l TOC to a highof 100 mg/l TOC. It demonstrated the low biodegradabilitycharacteristics of aniline, and further that no obvious inhibition ofdenitrification rates by aniline were observed in that range of initialaniline concentrations.

Having now fully described the present invention in some detail by wayof illustration and example for purposes of clarity of understanding, itwill be obvious to one of ordinary skill in the art that same can beperformed by modifying or changing the invention with a wide andequivalent range of conditions, formulations and other parametersthereof, and that such modifications or changes are intended to beencompassed within the scope of the appended claims.

All publications, patents and patent applications mentioned in thisspecification are indicative of the level of skill of those skilled inthe art to which this invention pertains, and are herein incorporated byreference to the same extent as if each individual publication, patentor patent application was specifically and individually indicated to beincorporated by reference.

What is claimed is:
 1. An aquaculture system comprising: (a) an aqueousenvironment; (b) a means for fluidly connecting said aqueous environmentwith a biofilter system, said biofilter system comprising: (i) a mainbiofilter chamber having an inlet port and an outlet port and containingtherein aerobic and anaerobic bacteria without physical separation; and(ii) a means for oxygenating said aerobic and anaerobic bacteria in saidmain biofilter chamber, including means for timing the oxygenation ofsaid aerobic and anaerobic bacteria; (c) a means for disinfecting anoutflow of said biofilter system; and (d) a means for returning saiddisinfected outflow to said aqueous environment.
 2. The aquaculturesystem of claim 1, wherein said aquaculture system further comprises apump.
 3. The aquaculture system of claim 1, wherein said aquaculturesystem further comprises a means for filtering an outflow from saidaqueous environment.
 4. The aquaculture system of claim 1, wherein saidaqueous environment is a tank.
 5. The aquaculture system of claim 1,wherein said aqueous environment is a natural or a man-made pond.
 6. Theaquaculture system of claim 1, wherein said aqueous environment is anatural or a man-made lake.
 7. The aquacultrue system of claim 1,wherein said aqueous environment is a cage system on a river, anear-shore area and/or a fjord.
 8. A method of aquaculture, wherein fishare grown in said aqueous environment of claim
 1. 9. A system fortreating animal waste comprising: (a) a first vessel having a firstinlet port and a first outlet port, wherein said first vessel containsmeans for degrading animal waste solids within said animal waste andmeans for separating animal waste solids and animal waste liquid; and;(b) a second vessel comprising a biofilter system wherein an inlet portof said biofilter chamber is fluidly connected to said first outlet portof said first vessel, and wherein said biofilter system comprises: (i) amain biofilter chamber having an inlet port and an outlet port andcontaining therein aerobic and anaerobic bacteria without physicalseparation; and (ii) a means for oxygenating said aerobic and anaerobicbacteria in said main biofilter chamber, including means for timing theoxygenation of said aerobic and anaerobic bacteria.
 10. The system fortreating animal waste of claim 9, wherein an effluent from said firstvessel is aqueous.
 11. A method of removing carbonaceous matter,nitrogenous matter, or mixtures thereof from animal waste, comprisingpassing said animal waste through said system for treating animal wasteof claim
 9. 12. The method for removal of claim 11, wherein an amount ofsaid carbonaceous matter, nitrogenous matter, or mixtures thereof insaid outflow is reduced by no less than approximately 80% from anoriginal amount of said carbonaceous matter, nitrogenous matter, ormixtures thereof in said liquid portion of said animal waste.
 13. Themethod for removal of claim 12, wherein the amount of said carbonaceousmatter, nitrogenous matter, or mixtures thereof in said outflow isreduced by no less than approximately 90% from the original amount ofsaid carbonaceous matter, nitrogenous matter, or mixtures thereof insaid liquid portion of said animal waste.
 14. The method for removal ofclaim 11, wherein said animal waste is produced by any one of a pig, ahorse, a goat, a sheep, a cow, a chicken, a turkey, an ostrich, an emu,a llama or an alpaca.
 15. The method for removal of claim 11, whereinsaid animal waste comprises no more than approximately 10% solid animalwaste.
 16. The method for removal of claim 15, wherein said animal wastecomprises no more than 5% solid animal waste.
 17. The method for removalof claim 16, wherein said animal waste comprises no more thanapproximately 1% solid animal waste.